Run-flat pneumatic tire assembly and method

ABSTRACT

A run-flat pneumatic tire assembly includes a pneumatic tire having an elastomeric casing and a tire cavity formed therein. A longitudinally-extending and approximately planar length of strip material is helically arranged within the tire cavity to pre-stress the length of strip material for usage of the pneumatic tire during under-inflated and non-inflated conditions. A method of making a run-flat pneumatic tire assembly is also included.

This is a divisional of U.S. patent application Ser. No. 12/364,951filed on Feb. 3, 2009, which is hereby incorporated herein by referencein its entirety.

The subject matter of the present document broadly relates to the art ofrun-flat pneumatic tires and, more particularly, to a pneumatic tire andstructural insert assembly that is adapted for run-flat operation aswell as a method of making the same.

INCORPORATION BY REFERENCE

The entire disclosure of U.S. Pat. Nos. 4,428,411; 4,459,167; and6,405,773 are hereby incorporated herein by reference.

BACKGROUND

One area of tire technology that has been developed during the last fewdecades is the concept of a pneumatic tire that is capable of operatingin an under-inflated or non-inflated condition. In such types ofpneumatic tires, which are often referred to in the industry as“run-flat” tires, it is generally desired for an under-inflated ornon-inflated tire to support a vehicle during operation for apredetermined minimum number of miles and at speeds up to apredetermined maximum speed of operation. The advantages of such a tirein safety and convenience are well documented.

One example of a run-flat tire construction that has been developed overthe years is the band-reinforced radial tire, which was invented by theinventor of the present application. Typically, a banded run-flat tireis a pneumatic radial tire having a casing with a crown and sidewallsextending from the crown on either side to annular beads which, in aconventional way, are used to mount the tire in a sealed relationship onthe rim of a wheel. The band element is embedded in the crown of thetire underlying the tread during the manufacture of the tire while thetire is in a green or uncured state. In some cases, the band element maybe a thin structural ring of high-strength steel or a fiber/epoxycomposite, such as is disclosed in U.S. Pat. Nos. 4,111,249; 4,318,434;4,456,048; 4,734,144; 5,879,484; 6,112,791; 6,117,258; 6,148,885;6,321,808; 6,363,986; 6,405,773; 6,420,005; 6,436,215; 6,439,288;6,460,586; 6,470,937 and 6,598,634, for example. In other cases, theband element may take the form of a helical structure or coiled member,such as is disclosed in U.S. Pat. Nos. 4,673,014; 4,708,186 and4,794,966, for example.

Another example of a run-flat tire construction involves the use of afinished or cured tire of an otherwise standard construction. In thistype of run-flat tire construction, a pre-curved, helical or coil-likestructural element is formed. The pre-curved coil-like structure is theninserted into the inner cavity of the finished tire in a suitablemanner, such as by winding up the helix to reduce the outside diameterthereof or by separating an end of the coil-like structure and feedingthe structure into the inner cavity due to relative rotation between thestructure and the tire. Such a run-flat tire construction is, forexample, disclosed in U.S. Pat. Nos. 4,428,411 and 4,459,167.

With reference to such known constructions, FIG. 13 of the presentapplication graphically illustrates relative stress levels that would beexpected to occur in known run-flat tire constructions that rely uponthe use of pre-curved bands. The general outline of a pre-curved band isindicated by reference number 50 in FIG. 13. Pre-curved band 50 is shownundergoing the deflection expected during use, with a ground contactpatch 52 being formed along a road or other surface 54. Additionally,FIG. 13 illustrates relative stress levels that would be expected to beexperienced by the pre-curved band during such use. Inner surfacestresses are represented by line 56 and outer surface stresses arerepresented by line 58 with compression being represented by lineportions disposed radially-inwardly from band 50 and tension beingrepresented by line portions disposed radially-outwardly from band 50.

It has been observed that conventional pre-curved bands operating withinan under-pressurized or non-pressurized tire will normally have thecapability (i.e., durability) to exceed a 100 mile performance target.However, it has also been recognized that such known pre-curved bandsmay provide less than the desired level of performance during normal,pressurized operation of the tire. It will be appreciated that duringnormal, pressurized operation, a pre-curved band could be subjected tocyclic flexing and corresponding cyclic variation in stresses many tensof millions of times to reach an 80,000 mile performance target.

It is believed that one reason for the less than optimal level ofperformance of known pre-curved bands during pressurized operationinvolves the relative variation in stresses to which known bands aresubjected during use. That is, it has been determined that the curvatureof pre-curved bands forward and aft of the ground contact area resultsin relatively low stresses being included in these fore and aft areas.In FIG. 13, pre-curved band 50 would rotate in the direction of arrow RTwith areas forward of ground contact patch 52 being indicated byreference characters FWD and areas aft of ground contact patch 52 beingindicated by reference characters AFT. It has also been determined,however, that while a given portion of a pre-curved band is disposedwithin the ground contact area, the pre-curved band is flexed from theinitially pre-curved condition into an approximately flat state. Duringthis approximately flat condition, the stresses within the pre-curvedband may be substantially higher than the relatively low stresses in thefore and aft areas. What's more, if a positive obstacle is encounteredby the tire, the resulting stresses in the pre-curved band at the groundcontact area will be further increased.

Furthermore, it is well understood that tension/compression-type cyclicloading can accelerate the decrease in performance of load bearingmembers, such as may be due to material fatigue, for example. It will berecognized from FIG. 13 that in areas forward of ground contact patch52, stresses along inner surface 56 of pre-curved band 50 are due tocompression and that stresses along outer surface 58 are due to tension.As pre-curved band 50 approaches ground contact patch 52, however, anarea of deflection 60 is reached at which the load conditions arereversed and stresses along inner surface 56 are due to tension withstresses along outer surface 58 being due to compression. As pre-curvedband 50 exits ground contact patch 52, another area if deflection 62 isreached in which the load conditions are again reversed such thatstresses along the point on inner surface 56 are again due tocompression and stresses at the corresponding point on the outer surfaceare again due to tension. As such, known pre-curved bands are typicallyexposed to a cyclic load condition during each rotation of tire and itis believed that such cyclic loading may contribute to any decreasedperformance of such pre-curved bands.

Although known run-flat pneumatic tire constructions generally operatesatisfactorily, the desire remains to increase performance (e.g.,run-flat mileage, pressurized mileage and maximum speed of run-flatoperation) and reduce manufacturing costs. As such, the subject conceptseeks to provide these and other benefits and/or improvements over knownrun-flat pneumatic tire constructions.

BRIEF DESCRIPTION

A run-flat pneumatic tire assembly in accordance with the subject matterof the present disclosure is provided that includes a pneumatic tire anda pre-stressed structural insert. The elastomeric casing is disposedcircumferentially about an axis and includes a crown portion and a pairof axially-spaced sidewalls extending radially inwardly from along thecrown portion. The crown portion includes an outer surface and an innersurface that at least partially defines a tire cavity. The pre-stressedstructural insert including a longitudinally-extending and approximatelyplanar length of strip material having first and secondlongitudinally-extending sides defining a strip material thickness andopposing longitudinally-extending edges defining a strip material width.The length of strip material is disposed within the tire cavity in ahelical arrangement such that the first side is facing outwardly towardthe inner surface of the crown portion. The structural insert ispre-stressed due to at least the helical arrangement of the length ofstrip material within the tire cavity. This pre-stressed arrangementestablishes a theoretical neutral plane along said length of stripmaterial between the first and second sides thereof with the first sideof the length of strip material being in tension and the second side ofthe length of strip material being in compression.

A run-flat pneumatic tire according to the foregoing paragraph is alsoprovided in which the length of strip material can be formed from aplurality of strand elements and a matrix material that at leastpartially encapsulates the plurality of strand elements.

A run-flat pneumatic tire according to the foregoing paragraph isfurther provided in which a non-zero percentage of the plurality ofstrand elements can have a lengthwise portion that extends at a non-zeroangle with respect to the neutral plane thereby minimizing formation ofmatrix-only planes that extend in approximate alignment with the neutralplane.

A method of making a run-flat pneumatic tire assembly in accordance withthe subject matter of the present disclosure is provided that includesproviding a pneumatic tire. The pneumatic tire includes an elastomericcasing having a crown and opposing sidewalls. The crown includes anouter surface and an inner surface that at least partially defines atire cavity. The method also includes forming a longitudinally-extendingand approximately-planar length of strip material having first andsecond longitudinally-extending sides defining a strip materialthickness and opposing longitudinally-extending edges defining a stripmaterial width. The method further includes inserting the length ofstrip material into the tire cavity in a helical arrangement such thatthe first longitudinally-extending side is facing outwardly toward theinner surface of the crown portion and thereby forming a structuralinsert that is pre-stressed due at least in part to the helicalarrangement of the approximately planar length of strip material.

A method according to the foregoing paragraph is also provided in whichthe action of forming the longitudinally-extending andapproximately-planar length of strip material can include gathering theplurality of strand elements into a bundle and forming the bundle into across-sectional shape having the strip material thickness and the stripmaterial width.

A method according to the foregoing paragraph is also provided in whichthe action of forming the longitudinally-extending andapproximately-planar length of strip material can include twisting thebundle of the plurality of strand elements such that a non-zeropercentage of the plurality of strand elements have a lengthwise portionwith a directional component extending in approximate alignment with thestrip material thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional side view of one exemplaryembodiment of a pneumatic tire and structural insert assembly inaccordance with the subject matter of the present document.

FIG. 2 is a diagrammatic cross-sectional side view of another exemplaryembodiment of a pneumatic tire and structural insert assembly inaccordance with the subject matter of the present document.

FIG. 3 is a graphical representation of a run-flat pneumatic tire inaccordance with the subject matter of the present document illustratingexemplary stresses experienced during run-flat operation.

FIG. 4 is an enlarged diagrammatic cross-sectional side view of anexemplary length of strip material suitable for use as a structuralinsert in accordance with the subject matter of the present disclosure.

FIG. 5 is a diagrammatic perspective view of two exemplary twistedstrand elements.

FIG. 6 is a diagrammatic perspective view of a section of one exemplarylength of strip material in accordance with the subject matter of thepresent disclosure.

FIG. 7 is a diagrammatic cross-sectional side view of the exemplarystructural insert in FIG. 6 taken at section 7-7 thereof.

FIG. 8 is a diagrammatic cross-sectional side view of the exemplarystructural insert in FIG. 6 taken at section 8-8 thereof.

FIGS. 9-11 diagrammatically represent one portion of an exemplary methodof installing a length of strip material into a pneumatic tire for useas a structural insert in accordance with the subject matter of thepresent document.

FIG. 12 graphically represents one exemplary method of making apneumatic tire and structural insert assembly in accordance with thesubject matter of the present document.

FIG. 13 is a graphical representation of a known run-flat pneumatic tireillustrating exemplary stresses experienced thereby during run-flatoperation.

DETAILED DESCRIPTION

Turning now to the drawings wherein the showings are provided for thepurpose of illustrating exemplary embodiments of the subject matter ofthe present disclosure and which drawings are not intended to belimiting, FIG. 1 illustrates a run-flat pneumatic tire assembly 100 thatincludes a pneumatic tire 102 and a structural insert 104 adapted topermit operation of the pneumatic tire in an under-inflated ornon-inflated condition. It will be appreciated that the pneumatic tirecan be of any suitable type, kind, construction and/or configuration.Additionally, the pneumatic tire can be formed from any suitablematerial or combination of materials, such as cured rubber or castpolyurethane, for example.

In the exemplary arrangement shown in FIG. 1, pneumatic tire 102 isshown mounted on a wheel 106, which can be of any suitable type, kind,construction and/or configuration, such as conventional arrangementhaving a drop center hub 108 welded to a circumferentially-extending rim110. Tire 102 extends circumferentially about an axis (not shown) andincludes an elastomeric casing 112 that has a crown portion 114 andaxially-spaced sidewalls 116 that extend radially inwardly from alongcrown portion 114. The crown portion includes an outer surface 118 andan inner surface 120 that at least partially defines a tire cavity 122.Grooves 124 can be provided along outer surface 118 of crown portion 114in any desired pattern or configuration to form a tire tread, as is wellknown in the art.

As indicated above, pneumatic tire 102 can be of any suitable type,kind, construction and/or configuration. For example, in the exemplaryarrangement shown in FIG. 1, pneumatic tire 102 includes bead portions126 that are adapted to seat in an air-tight relationship along rim 110,such as when pneumatic tire 102 is mounted on wheel 106. Bead portions126 can be reinforced with annular cords or wires 128 in a conventionalmanner. Radial tires, as is well known, include one or more pliescontaining a multiplicity of closely spaced radial reinforcing cords orwires in the sidewalls of the tires. In the exemplary arrangement inFIG. 1, sidewalls 116 are shown as being reinforced by weftless radialplies or elements 130. Further reinforcement of the tire can be providedby one or more annular belts, such as belt 132 extendingcircumferentially along crown portion 114, for example. Elements 130 andbelt 132 can be fabricated of any suitable material or combination ofmaterials, such as steel wires or suitable textile fibers, for example,as is well known in the art. When mounted on a wheel, pneumatic tire 102can be inflated through a conventional valve (not shown) that isoperatively connected with tire cavity 122, such as through rim 110 ofwheel 106, for example.

Structural insert 104 is formed from a longitudinally-extending andapproximately-planar length of strip material 134 that is helicallyarranged within the tire cavity of the associated pneumatic tire.Preferably, length of strip material 134 is a generally straight andapproximately flat strip of material. Length of strip material 134includes first and second longitudinally extending sides 136 and 138that define a strip material thickness, which thickness is representedin FIG. 1 by dimension ST1. Length of strip material 134 also includesopposing, longitudinally-extending edges 140 and 142 that define a stripmaterial width, which width is represented in FIG. 1 by referencedimension SW1.

In the exemplary arrangement shown in FIG. 1, length of strip material134 is helically arranged within tire cavity 122 such that first side136 is disposed in facing relation to inner surface 120 of crown portion114. In such a helical arrangement, length of strip material 134 isformed into a plurality of coils or loops 144 such that the full lengthof strip material fits within the tire cavity of the associatedpneumatic tire. In the exemplary arrangement shown in FIG. 1, the edgesof adjacent coils are disposed in close relation for abutting engagementwith one another such that minimal gaps are formed between the adjacentcoils.

An alternate embodiment of a run-flat pneumatic tire 100′ is shown inFIG. 2 in which a structural insert 104′ is shown disposed withinpneumatic tire 102. It will be appreciated that structural insert 104′is generally similar to structural insert 104 discussed above withregard to FIG. 1. As such, like features and/or elements in FIG. 2 willbe identified by identical numbers to those used in FIG. 1 and new ordifferent features and/or elements in FIG. 2 will be identified byprimed (′) reference numbers.

More specifically, structural insert 104′ is also formed from alongitudinally-extending and approximately-planar length of stripmaterial 134′ that is helically arranged within the tire cavity of theassociated pneumatic tire. While length of strip material 134′ (as wellas length of strip material 134) is preferably formed as a generallystraight and approximately flat strip of material, the length of stripmaterial could alternately have some amount of curvature in a free orotherwise unflexed condition, such as is schematically represented inFIG. 9, for example. Also, structural insert 134′ is shown as differingfrom structural insert 134 in both thickness and width, as isrepresented by reference dimensions ST2 and SW2, respectively, as wellas in overall length (not shown) which results in a reduced number ofloops or coils formed within the tire cavity.

Length of strip material 134′ is also helically arranged within tirecavity 122 such that first side 136 is disposed in facing relation toinner surface 120 of crown portion 114. In such a helical arrangement,length of strip material 134′ is formed into a plurality of coils orloops 144′ such that the full length of strip material fits within thetire cavity of the associated pneumatic tire. In the exemplaryarrangement shown in FIG. 2, the edges of adjacent coils are disposed inaxially-spaced relation to one another such that a single helical grooveextends along the length of strip material. The single helical grooveforms axially-spaced gaps 146′ between edges of adjacent coils.

One or more spacer elements 148′ can optionally be included, such as toevenly space adjacent coils during installation and/or to maintain theaxially-spaced alignment during subsequent assembly processes. The oneor more spacer elements can be provided in any suitable form,arrangement and/or configuration. As one example, a plurality ofindividual spacer elements could be installed within the helical grooveat various circumferential and/or axial positions therealong. As anotherexample, one or more spacer members 150′ could optionally be providedthat include a plurality of spacer elements extending therefrom. In suchan arrangement, the spacer elements would preferably be spaced apartfrom one another a distance approximately equal to the strip materialwidth. Though only one spacer member 150′ is shown in FIG. 2, it will beappreciated that any suitable number of two or more spacer members couldbe used, such as being circumferentially spaced from one another alongsecond side 138 of structural insert 104, for example. As one example,the spacer members could be positioned about 30 degrees apart around theinner circumference of the structural insert. What's more, spacerelements 148′ and/or spacer members 150′ can be formed from any suitablematerial or combination of materials, such as a PVC plastic or othersuch thermoplastic material, for example. And, the spacer elementsand/or spacer members can be temporarily installed for assembly purposesor can be adhesively or otherwise secured into place in a permanentmanner.

In order to maintain a pneumatic tire in an operational state after thetire has become under-pressurized or even non-pressurized, ahigh-strength structural support element (e.g., structural inserts 104and 104′) can be installed within an existing pneumatic tire (e.g., tire102), such as a finished and fully-cured rubber radial tire, forexample. In the present case, it is expected that a pneumatic tire willbe capable of operating at normal deflection under approximatelyone-half the normal operating pressure of the tire while retaining allof the desired performance and handling characteristics, when fittedwith a structural support element in accordance with the presentdisclosure. As illustrated above, such a high-strength structuralsupport element will preferably be installed within the cavity of thetire casing such that the structural element is disposed inapproximately coaxial relation to the crown portion of the tire casing.

Additionally, such a high-strength structural support element willpreferably be pre-stressed when installed into the tire cavity, such as,for example, by providing a longitudinally-extending and approximatelyplanar length of strip material and inserting the same into a tirecavity in a helical arrangement. As illustrated in FIG. 3, it isexpected that the use of the structural insert in the pre-stressedcondition will greatly reduce the relative stresses in the groundcontact area and thereby significantly increase pressurized performanceof the structural insert in comparison with known pre-curved bands.

With further reference to FIG. 3, a high-strength structural supportelement in accordance with the present disclosure can be approximatelyflat (or, in some cases, slightly curved) prior to installation but willbe highly flexed when installed in a helical arrangement within the tirecavity. Once installed, the highly-flexed structural support elementwill deflect during use in a substantially conventional manner, as isrepresented by item number 200 in FIG. 3. As is also illustrated in FIG.3, however, it is expected that the relative stress levels in astructural support element according to the present disclosure withdiffer significantly from the relative stress levels discussed above forknown pre-curved bands. As described above with respect to pre-curvedband 50, structural support element 200 will also include a groundcontact patch 202 formed along a road or other surface 204.Additionally, similar conventions to those used in connection with FIG.10 are used to describe FIG. 3, with inner surface stresses ofstructural support member 200 being represented by line 206 and outersurface stresses of the structural support member being represented byline 208. Furthermore, compression is represented in FIG. 3 by lineportions disposed radially-inwardly from structural support element 200and tension is represented by line portions disposed radially-outwardlyfrom structural support element 200.

As mentioned above, coiling the initially-flat structural supportelement will generate the desired pre-stressed condition in thestructural support element when installed. As a result, inner surfacestresses 206 of a structural support element according to the subjectdisclosure are shown in FIG. 3 as being different from inner surfacestresses 56 of known pre-curved band constructions in that in areas foreand aft of ground contact patch 202, inner surface stresses 206 areexpected to be increased relative to inner surface stresses 56.Similarly, outer surface stresses 208 of a structural support element ofthe subject disclosure are shown as being different from inner surfacestresses 58 of known pre-curved band constructions in that in areas foreand aft of ground contact patch 202, inner surface stresses 206 are alsoexpected to be increased over stresses 56. Such increases in the subjectstructural support element will generally be attributable to lack ofinitial curvature and the overall pre-stressed condition of the subjectstructural support element when installed in a tire.

During operation and use of the tire, however, a portion of thepre-stressed structural support element will return to theapproximately-flat initial condition when in the ground contact area 202(i.e., will approximately match the road surface). As such, it isexpected that this portion of the structural support element will besubjected to very low stresses (e.g., a near-zero stress level) whenwithin the ground contact area. This is illustrated in FIG. 3 by lines206 and 208 being disposed on-top-of or otherwise very near line 200representing the structural support element. As such,tension/compression-type cyclic loading can be minimized or evenavoided, which is expected to positively impact pressurized durabilityof the run-flat tire as well as under-pressurized or non-pressurizedperformance endurance. Additionally, if a positive obstacle were to beencountered by a run-flat tire utilizing the subject pre-stressedstructural support element (e.g., structural inserts 104 and 104′), theresulting stresses in the ground contact area would be expected to besubstantially lower in comparison to the resulting stresses in apre-curved band under similar conditions.

One effect of the installation of such a pre-stressed structural supportelement within the tire casing is that the tire casing may be placedinto tension by the structural element. This pre-stresses the tirecasing and can act as a partial replacement of the normal operatingpressure of the tire. During run-flat operation, the radial cords orwires of the tire function as spoke-like reinforcing elements and act astension members to support vehicle loads. The radial spoke-like elementsextend across the high-strength structural support element to form aload-sustaining structure, such as may be analogous to an elastic arch.Thus, the high-strength structural support element receives the loadsfrom the radial cords or wires and carries these loads to the road orground surface in compression and bending.

For convenience and ease of reading, reference will be primarily madehereinafter to length of strip material 134 without specific referenceto length of strip material 134′. However, it is to be understood thatany features, elements and/or other aspects discussed in connection withlength of strip material 134 will be equally applicable to length ofstrip material 134′.

Length of strip material 134 can be formed from any suitable material orcombination of materials and can be manufactured by way of any one ormore processes or methods that may be suitable for generating elongatedlengths of approximately planar material. In one preferred arrangement,length of strip material 134 is formed from a plurality of strand-likeelements 152 that are at least partially encapsulated within a binder ormatrix material 154, as shown in FIG. 4. At any given cross section, theplurality of strand elements may be arranged such that a nestingrelationship is formed between the strand elements in one row and thestrand elements in at least one row adjacent thereto, as indicated byreference dimension OVL. In this manner, at least some portion of thestrand elements from each of two adjacent rows will overlap one anotherand might thereby help to avoid the formation of a plane or path that isformed only of matrix or resin material. As discussed hereinafter, it isdesirable to avoid or minimize the formation of resin only planes thatare in approximate alignment with a longitudinally-extending neutralplane NP of length of strip material 134. Rather, a path of resin ormatrix material would follow wavy line WLN.

It will be recognized that any suitable binder or matrix material can beused, such as a thermoplastic or a thermoset, for example. Optionally, atoughening agent or other additives can be combined with the matrixmaterial in a suitable quantity, such as from approximately 5 percent toabout 40 percent, for example. One example of a suitable tougheningagent that could be used is carboxy-terminated nitrile rubber (CTBN).Examples of toughened epoxy resins that may be suitable for use informing a length of strip material in accordance with the subjectdisclosure are available from Hexion Specialty Chemicals of Columbus,Ohio under the trade name EPON.

It will be appreciated that the plurality of strand-type elements cantake any suitable shape, form, configuration and/or arrangement. Forexample, a strand element could take the form of a single filament(i.e., monofilament) formed from a single material. As another example,a strand element could be formed from a plurality of filaments or fibersthat together form a strand element. Also, it will be appreciated thatsuch a plurality of fibers can be in any configuration and/orarrangement, such as being braided or unbraided, twisted or untwisted,and/or free or attached fibers (i.e., a plurality of fibers that areadhesively connected to one another). For example, the plurality ofstrand elements used to form length of strip material 134 couldoptionally include one or more of strand elements 152A that are formedfrom fibers 156A, as shown in FIG. 5. Additionally, or in thealternative, the plurality of strand elements used to form length ofstrip material 134 could optionally include one or more of strandelements 152B that are formed from fibers 156B. It will be appreciatedthat strand elements 152A and 152B are twisted in a helical manner todifferent levels of tightness or degrees of twist. For example, fibers156A could have a twist oriented at an angle to the circumference thatis preferably within the range of approximately 20 degrees toapproximately 60 degrees. As another example, fibers 156B could have atwist oriented at an angle to the circumference that is preferablywithin the range of approximately 0 degrees to approximately 25 degrees.However, it will be appreciated that strands of any suitable arrangementor combination of arrangements can be used.

Additionally, it will be appreciated that such a plurality of fibers canbe formed from any suitable type or kind of material or combination ofmaterials, such as, for example, fiberglass fibers, aromatic polyamidefibers, carbon fibers or any combination thereof. It will be furtherappreciated that such strand elements can be of any suitable lengthand/or cross-sectional dimension (e.g., width, thickness and/ordiameter). As one example, a plurality of individual carbon fibershaving a cross-sectional dimension (e.g., a diameter) within a range ofapproximately 0.00002 inches to 0.00005 inches could be used to formstrand elements having a cross-sectional dimension (e.g., a diameter)within a range of approximately 0.0001 inches to 0.005 inches. Aplurality of such strand elements could then be used to form a length ofstrip material, such as length of strip material 134, for example. Itwill be appreciated, however, that the foregoing example is merelyillustrative and that any other suitable construction could alternatelybe used.

As discussed above, length of strip material 134 is preferably formedfrom a plurality of strand elements. It will be appreciated that anysuitable number of strand elements can be used, such as from severalhundred strand elements to many millions of strand elements, forexample, depending upon the size, shape and construction of the lengthof strip material as well as the size, shape, construction andarrangement of the strand elements. For example, the number of strandelements used in forming a length of strip material can have a relationto a ratio of filament-to-matrix material that may be determined to beappropriate for the desired performance characteristics of the resultinglength of strip material. While it will be appreciated that any suitableratio can be used, one exemplary range includes ratios of fromapproximately 50/50 filament-to-matrix material to approximately 70/30filament-to-matrix material, with a ratio of approximately 60/40filament-to-matrix material being preferred.

For purposes of clarity and ease of understanding, length of stripmaterial 134 is shown in FIG. 6 with only a single strand element beingillustrated and identified by item number 152. Strand element 152extends from a first end 156 of the length of strip material to anopposing second end 158 thereof. It is preferred that each of theplurality of strand elements used to form the length of strip materialextends the full length thereof. In some cases, however, a percentage ofthe plurality of strand elements may either begin or end within a givenlength of strip material. It will be appreciated that, for purposes ofillustration only, both strand element 152 and length of strip material134 are shown in FIG. 6 in a broken or discontinuous fashion, whichassists in illustrating ends 156 and 158.

At first end 156 the beginning of strand element 152 is identified byreference character A in FIG. 6. Similarly, the end of strand element152 at second end 158 is identified by reference character B. Asdiscussed above, strand element 152 preferably extends continuously fromthe first end to the second end of the length of strip material. Due tothe broken illustration of length of strip material 134 in FIG. 6,strand element 152 is shown with a section extending between referencecharacters C and D being omitted. It will be appreciated that theplurality of strand elements used to form length of strip material 134can extend from first end 156 to second end 158 in any suitable mannerand along any desired and/or resulting path, such as may be intended orotherwise occur during manufacturing.

It will be recognized that length of strip material 134 will be flexedin a lengthwise manner during use, which will result in the formation ofa neutral axis extending widthwise across the length of strip materialto define a neutral plane NP (FIGS. 4, 7 and 8) that extends lengthwisealong the length of strip material. According to well understoodprinciples, the strand elements and matrix material on one side of theneutral plane (e.g., the side of the neutral plane that includes firstside 136) will be placed in tension and the strand elements and matrixmaterial on the other side of the neutral plane (e.g., the side of theneutral plane that includes second side 138) will be in compression. Ithas been determined that increased performance of a structural insert(e.g., structural insert 104) can be achieved if the occurrence of resinonly planes extending in approximate alignment with (e.g., approximatelyparallel to) the neutral plane are minimized or avoided. It will beappreciated, however, that the reduction or elimination of resin onlyplanes can be achieved in any suitable manner.

As one example, a quantity of the plurality of strand elements caninclude a portion or lengthwise section that extends in the direction ofthe thickness of the length of strip material such that the generationof resin only planes, particularly those disposed in approximatealignment with the neutral plane, can be minimized or avoided. That is,at least some amount (i.e., a non-zero number) of the plurality ofstrand elements include at least a portion or lengthwise section thatextends in a direction that is disposed at an angle to or otherwise notaligned with the neutral plane (e.g., at a non-zero angle with respectto the neutral plane). A non-zero number of the plurality of strandelements that are disposed at such an angle can, for example, be withina range of approximately 3 percent to approximately 99 percent of theplurality of strand elements. For example, a lengthwise portion of atleast some quantity of the plurality of strand elements could extendalong an approximately linear path but be disposed at non-zero angles tothe neutral plane. As another example, a lengthwise portion of at leastsome quantity of the plurality of strand elements could extend along acurved or otherwise non-linear path with respect to the thickness of thelength of strip material and, thus, have a directional component thatextends in the thickness direction. In either case, a lengthwise portionof at least some quantity of the plurality of strand elements willinclude a change in relative position and/or orientation with respect toat least the direction of thickness (e.g., thicknesses ST1 and ST2) ofthe length of strip material. What's more, in some cases, a lengthwiseportion of at least some number of the plurality of strand elements mayextend across the neutral plane. That is, a lengthwise portion of atleast some quantity of the plurality of strand elements can extend fromalong one side of the neutral plane, across the neutral plane to theother side thereof.

An example in which a lengthwise portion of a quantity of the pluralityof strand elements has a curved or otherwise non-linear path isillustrated in FIGS. 6-8. As discussed above with respect to FIG. 6,strand element 152 extends lengthwise along length of strip material 134between first and second ends 156 and 158, as indicated by referencepoints A and B. Strand element 152 is shown in FIGS. 6 and 7 as having arelative position, at a reference point E, with respect to the thicknessof the length of strip material, as is indicated by reference dimensionPS1 (FIG. 7). Strand element 152 shown in FIGS. 6 and 8 as having arelative position, at a reference point F, with respect to the thicknessof the length of strip material, as is indicated by reference dimensionPS2 (FIG. 8). As such, at least a lengthwise portion of strand element152 is shown extending in the direction of the thickness of length ofstrip material 134. This results is a variation or change in therelative orientation or thickness position of strand element 152, as isindicated by reference dimension DPS in FIG. 8.

In the arrangement shown in FIGS. 6-8, strand element 152 extends alonga non-linear and/or non-uniform path that crosses from along one side ofneutral plane NP to along the other side of the neutral plane at leastonce. It will be recognized, however, that, in practice, some number orquantity of strand elements may be disposed in approximate alignmentwith the neutral plane, some other number or quantity of strand elementsmay have a lengthwise portion that includes a relatively small change inposition with respect to the thickness of the length of strip material,and still some further number of strand elements may have a lengthwiseportion that extends across the neutral axis. As a result, the foregoingconstruction and/or arrangement will likely result in the desiredminimization of resin only planes in the length of strip material. And,it is expected that performance of the structural insert will increaseas the number or quantity of strand elements that are in the latter twocategories increases.

It is indicated above that inner surface stresses 206 and outer surfacestresses 208 of the subject structural insert are increased over theinner and outer surface stresses of known pre-curved bands. However, itwill be appreciated that the use of a composite construction for thelength of strip material, such as that discussed above, for example, isexpected to result in a structural insert having operating stresseswithin the endurance fatigue limit of the material. As one example, sucha material may provide a stiffness equivalent within a range ofapproximately 25×10⁶ lbs-in² to approximately 30×10⁶ lbs-in² (Young'sModulus×moment of inertia).

As indicated above, length of strip material 134 can be formed orotherwise manufactured using any one or more processes or methods. Oneexample of a suitable process is commonly referred to as a pultrusionprocess, which utilizes well established and existing technology. Theutilization of the pultrusion process may result in reducedmanufacturing costs associated the fabrication of the length of stripmaterial. Another benefit of the use of a longitudinally-extending andapproximately flat length of strip material is that the use of unique orspecially designed mandrels can be avoided, whereas such mandrels arenormally used in forming known pre-curved bands.

Turning, now, to FIGS. 9-11, a sequence of illustrations are showncorresponding to a process of installing length of strip material 134(or 134′) into the cavity of pneumatic tire 102. In FIG. 9, first end156 of the length of strip material, which is in an approximately flator an optional curved arrangement, is introduced into the cavity ofpneumatic tire 102. Relative rotation between length of strip material134 and pneumatic tire 102 results in deflection of first end 156 of thelength of strip material as the same makes contact with the innersurface of the elastomeric casing, as shown in FIG. 10. It will beappreciated that the relative rotation can be accomplished in anysuitable manner, such as by rotating the pneumatic tire about an axis AXas indicated by arrow AR1, for example. As the relative rotation betweenthe length of strip material and the pneumatic tire continues, such asis represented by arrow AR2, the length of strip material can be fed, inthe direction of arrow AR3 (FIG. 10), into the cavity of the tire untilsecond end 158 is reached and the entire length of strip material ishelically arranged within the tire cavity, as shown in FIG. 11.

FIG. 12 is a graphical representation of one exemplary method 300 ofmanufacturing a run-flat pneumatic tire assembly in accordance with thesubject matter of the present disclosure, such as pneumatic tireassembly 100, for example. Method 300 includes providing a cured,finished or otherwise complete pneumatic tire, such as a conventionalradial tire, for example, as indicated in box 302. Method 300 alsoincludes forming a length of strip material, such as length of stripmaterial 134 or 134′, for example, by way of a suitable manufacturingprocess, as indicated in box 304. Additionally, method 300 includesinserting the length of strip material into the cavity of the pneumatictire in a helical arrangement to form a pre-stressed structural insertsuitable for permitting operation of the pneumatic tire inunder-inflated or non-inflated conditions, as indicated in box 306.

Method 300 can optionally include securing the length of strip materialon or along an inner surface of the pneumatic tire. Such a securementaction can be performed in any suitable manner and by way of anysuitable materials and/or devices. For example, an adhesive (not shown)could be interposed between the outer surface of the length of stripmaterial and the inner surface of the casing of the pneumatic tire toproduce an interconnection therebetween, such as is indicated by box308. By securing the length of strip material on or along the innersurface of the pneumatic tire, the tire reinforcing elements act tocreate a composite beam structure with the reinforcing elementsconstituting an outer cap and the length of strip material forming theinner cap. In such an arrangement, a length of strip material having areduced strip material thickness may be used. Additionally, it will beappreciated that any suitable adhesive substance or material could beused, such as a heat activated adhesive material. As such, method 300can also optionally include heat curing the adhesive material to securethe length of strip material on or along the inner surface of the tire,as indicated in box 310.

Method 300 can also optionally include preloading the structural insertand pneumatic tire prior to the length of strip material that forms thestructural insert being secured on or along the pneumatic tire, as isindicated in box 312. Such a preloading action can be accomplished inany suitable manner. For example, an innertube can be placed within thetire cavity of the elastomeric casing after the length of strip materialhas been inserted. The innertube can then be pressurized to a suitablepressure level, such as approximately twice the rated tire pressure, forexample, to expand the elastomeric casing and preload the structuralinsert and the reinforcing elements of the tire. A parting surface, suchas a suitable spray film, for example, can be applied on or along theinnertube to minimize adhesion.

As discussed above, a length of strip material, such as length of stripmaterial 134 or 134′, for example, can be formed in any suitable mannerand through the use of any suitable actions or processes. As oneexample, the action of forming a length of strip material represented bybox 304 of method 300 can include providing a plurality of strandelements, as indicated by box 314. It will be appreciated that theplurality of strand elements can be provided in any suitable manner,such as by supplying extended lengths of filament material (e.g.,monofilament or numerous individual filaments) on a plurality of creelsor spools, for example. The action of forming a length of strip materialrepresented by box 304 can also include gathering the plurality ofstrand elements into a bundle as the filament material is feed from theplurality of creels or spools, as is indicated by box 316. The extendedlengths of filament material can act to supply substantially continuouslengths of strand elements that can be substantially continuouslygathered into a bundle.

The action of forming a length of strip material represented by box 304of method 300 can further include an optional action of varying orotherwise re-orienting at least a portion of the plurality of strandelements, as indicated by box 318 in FIG. 12. Such an action can beaccomplished in any suitable manner, such as by continuously twistingthe bundle of strand elements through a suitable angle with respect tothe circumference of the bundle, for example. While it will beappreciated that any suitable angle of twist could be used, oneexemplary range is from approximately 1 degree to approximately 20degrees, with an angle of approximately 10 degrees being preferred.

The action of forming a length of strip material represented by box 304of method 300 can further include an action of embedding or otherwiseencapsulating the plurality of strand elements in a binder or matrixmaterial, as indicated by box 320 in FIG. 12. Again, it will beappreciated that this can be accomplished in any suitable manner, suchas by coating the plurality of strand elements in the matrix material atone or more points in the process. An optional step of sizing theplurality of strand elements (or the filament material thereof) can alsobe included, such as to improve the wetting of the strand elements bythe matrix material. The action of forming a length of strip materialrepresented by box 304 of method 300 can still further include an actionof generating an exterior shape of the length of strip material, asindicated by box 322, such as by pulling the plurality of strandelements and matrix material through a suitable die arrangement, forexample.

As used herein with reference to certain elements, components and/orstructures (e.g., “first sidewall” and “second sidewall”), numericalordinals merely denote different singles of a plurality and do not implyany order or sequence unless specifically defined by the claim language.

While the subject novel concept has been described with reference to theforegoing embodiments and considerable emphasis has been placed hereinon the structures and structural interrelationships between thecomponent parts of the embodiments disclosed, it will be appreciatedthat other embodiments can be made and that many changes can be made inthe embodiments illustrated and described without departing from theprinciples of the subject novel concept. Obviously, modifications andalterations will occur to others upon reading and understanding thepreceding detailed description. Accordingly, it is to be distinctlyunderstood that the foregoing descriptive matter is to be interpretedmerely as illustrative of the present novel concept and not as alimitation. As such, it is intended that the subject novel concept beconstrued as including all such modifications and alterations insofar asthey come within the scope of the appended claims and any equivalentsthereof.

The invention claimed is:
 1. A method of making a run-flat pneumatictire assembly, said method comprising: a) providing a pneumatic tireincluding an elastomeric casing having a crown and opposing sidewalls,said crown including an outer surface and an inner surface that at leastpartially defines a tire cavity; b) providing a longitudinally-extendingand approximately-planar length of strip material having first andsecond longitudinally-extending sides defining a strip materialthickness and opposing longitudinally-extending edges defining a stripmaterial width with a first stress level along said first side, saidlength of strip material including a plurality of strand elements and amatrix material at least partially encapsulating said plurality ofstrand elements; and, c) inserting said length of strip material intosaid tire cavity in a helical arrangement such that said firstlongitudinally-extending side is facing outwardly toward said innersurface of said crown portion and thereby at least partially forming astructural insert that is pre-stressed due at least in part to areactive force applied to said helical arrangement of said approximatelyplanar length of strip material within said tire cavity by said tirewith said reactive force maintaining said length of strip material insaid helical arrangement resulting in a second stress level along saidfirst side that is greater than said first stress level.
 2. A methodaccording to claim 1 further comprising securing said length of stripmaterial in said helical arrangement along said inner surface of saidcrown portion of said tire.
 3. A method according to claim 2, whereinsecuring said length of strip material includes applying an adhesivealong at least one of said first side of said length of strip materialand said inner surface of said crown portion, and affixing said lengthof strip material along said inner surface using at least said adhesive.4. A method according to claim 2 further comprising applying pressure tosaid elastomeric casing and said length of strip material from withinsaid tire cavity to expand and thereby tension said elastomeric casingand said length of strip material prior to securing said length of stripmaterial in said helical arrangement along said inner surface of saidelastomeric casing.
 5. A method according to claim 1, wherein insertingsaid length of strip material in c) includes forming a plurality ofcoils from said length of strip material to form said helicalarrangement.
 6. A method according to claim 5, wherein forming saidplurality of coils includes abuttingly engaging opposing edges ofadjacent coils.
 7. A method according to claim 5, wherein forming saidplurality of coils includes axially-spacing said plurality of coils fromone another to form a gap between opposing edges of adjacent coils.
 8. Amethod according to claim 7 further comprising installing one or morespacer elements along said gap between said opposing edges of saidadjacent coils to maintain axial spacing between said adjacent coils. 9.A method according to claim 1, wherein providing alongitudinally-extending and approximately-planar length of stripmaterial in b) includes forming a longitudinally-extending andapproximately-planar length of strip material by at least gathering saidplurality of strand elements into a bundle and forming said bundle intoa cross-sectional shape having said strip material thickness and saidstrip material width.
 10. A method according to claim 9, wherein forminga longitudinally-extending and approximately-planar length of stripmaterial includes twisting said bundle of said plurality of strandelements such that a non-zero percentage of said plurality of strandelements have a lengthwise portion with a directional componentextending in approximate alignment with said strip material thickness.11. A method according to claim 1, wherein inserting said length ofstrip material in c) includes forming a structural insert with saidreactive force resulting in a theoretical neutral plane beingestablished along said length of strip material between said first andsecond sides thereof with said first side of said length of stripmaterial being in tension and said second side of said length of stripmaterial being in compression.
 12. A method of making a run-flatpneumatic tire assembly, said method comprising: a) providing apneumatic tire including an elastomeric casing having a crown andopposing sidewalls, said pneumatic tire including an inner surface andan outer surface, said inner surface at least partially defining a tirecavity, and said outer surface capable of forming a ground contact patchduring use on an associated ground surface; b) providing alongitudinally-extending and approximately-planar length of stripmaterial having first and second longitudinally-extending sides defininga strip material thickness and opposing longitudinally-extending edgesdefining a strip material width, and a first stress level along saidfirst side and a second stress level along said second side; and, c)inserting said length of strip material into said tire cavity in ahelical arrangement such that said first side is facing outwardly towardsaid inner surface to at least partially form a structural insert thatis pre-stressed by a reactive force applied to said helical arrangementwithin said tire cavity by said tire acting against said structuralinsert and preventing said structural insert from returning to alongitudinally-extending and approximately planar shape.
 13. A methodaccording to claim 12, wherein inserting said length of strip materialin c) includes forming a structural insert with said reactive forceresulting in a third stress level along said first side and a fourthstress level along said second side, said third stress level being atensile stress that is greater than said first stress level, and saidfourth stress level being a compressive stress that is greater than saidsecond stress level.
 14. A method according to claim 12, whereininserting said length of strip material in c) includes forming astructural insert with said reactive force resulting in a theoreticalneutral plane being established along said length of strip materialbetween said first and second sides thereof with said first side of saidlength of strip material being in tension and said second side of saidlength of strip material being in compression.
 15. A method according toclaim 14, wherein providing a longitudinally-extending andapproximately-planar length of strip material in b) includes forming alongitudinally-extending and approximately-planar length of stripmaterial from a plurality of strand elements and a matrix material atleast partially encapsulating said plurality of strand elements with anon-zero percentage of said plurality of strand elements having alengthwise portion extending at a non-zero angle with respect to saidneutral plane thereby minimizing formation of matrix-only planes thatextend in approximate alignment with said neutral plane.
 16. A methodaccording to claim 15, wherein forming said longitudinally-extending andapproximately planar length of strip material includes orienting saidplurality of stand elements such that said non-zero percentage of saidplurality of strand elements is within a range of from approximately 3percent to approximately 99 percent.
 17. A method according to claim 15,wherein forming said longitudinally-extending and approximately planarlength of strip material includes orienting said plurality of standelements such that said lengthwise portions of said non-zero percentageof said plurality of strand elements extend in a non-uniform andcurvilinear manner along said length of strip material.
 18. A methodaccording to claim 12, wherein inserting said length of strip materialin c) includes forming a plurality of coils from said length of stripmaterial to form said helical arrangement with adjacent ones of saidplurality of coils disposed in spaced relation to one another such thata gap is formed between opposing edges of adjacent coils.
 19. A methodaccording to claim 18 further comprising providing a spacer memberincluding a plurality of spacer elements that are disposed from oneanother at a distance approximately equal to said strip material width,said spacer member disposed along said second side of saidhelically-arranged length of strip material such that a different one ofsaid plurality of spacer elements is disposed within a gap betweenadjacent coils of said structural insert.
 20. A method according toclaim 12 further comprising securing said length of strip material tosaid pneumatic tire, securing said length of strip material includingdisposing an adhesive material between said first side of said length ofstrip material and said inner surface of said pneumatic tire andapplying pressure to said pneumatic tire and said length of stripmaterial from within said tire cavity to expand and thereby tension saidpneumatic tire and said length of strip material prior to securing saidlength of strip material in said helical arrangement along said innersurface.